1. Field of the Invention
The present invention relates generally to methods and apparatus for continuous winding of material at high speeds, and more particularly to an apparatus for transfer of material winding between spools wherein the spools are positioned in a co-planar configuration providing for material transfer to be accomplishing without crossing over a spool flange.
2. Description of the Prior Art
In order to maximize the economy of manufacture of elongated, spool wound material, it is necessary to configure the manufacturing process to allow continuous operation while transferring winding from a filled spool to an empty one. Shutting down the winding process to transfer between spools is time consuming and in some cases detrimental to product quality. For example, in the case of optical fiber production, the fiber is pulled from a molten billet of quartz by an apparatus called a draw machine. Disrupting or stopping the process is costly, since the drawing operation, once disturbed, must be started slowly and ramped back up to production speed. In addition to the lost time, material is wasted because the fiber made during the speed-increase ramp is largely thrown away. Because of this inefficiency, systems have been designed to accomplish a “flying transfer” wherein the fiber is wound onto an empty spool without stopping the drawing operation. U.S. Pat. No. 4,798,346 by Meyers et al. describes one such system wherein each spool has a mechanism called a collector. Meyers refers to the collector as a storage and clamping assembly, item 47 in reference to FIG. 7 of Meyers. The collector is embodied as two disk-like structures about the same diameter as the spool upon which the fiber is being wound. The collector disks are positioned adjacent a flange of each spool and rotate on the same axis as the flange and at the same velocity. Two spools are positioned in axial alignment, with their collector apparatus facing each other. During the winding process, both spools and collection assemblies are rotating at the same velocity. When the winding of fiber on one spool is complete, the distributor leads the fiber over the flange of the first spool and onto the collector assembly of the second spool. At this time the collector disks of the empty spool are open/spaced apart. A portion of the fiber is wound on an array of pins between the disks, whereupon the disks are clamped, securing the fiber. The distributor then guides the fiber over onto the empty spool and winding continues. A cutter is then extended to sever the fiber between the two spools, freeing the full spool for removal and replacement with an empty spool.
A variation of the collector system has the two spools radially offset. In this case, when the distributor moves the fiber onto the collector of the new spool, the fiber is clamped and quickly breaks due to the stretching action caused by relative motion of the collectors of the full spool and empty spool. A cutter bar can also be used in the system to sever the fiber between the spools. Once the fiber is broken, the transfer proceeds in the same manner as with axially offset systems.
Another variation of the collector system employs a snagger button mounted into the rotating portion of the spindel turning the spool. Upon transfer from a full spool to an empty spool, the distributor leads the fiber over the spool flange to the snagger button corresponding to the empty spool. On the next rotation of the spool, the snagger button snags the fiber and begins wrapping it around the empty spool. A cutter bar is extended and the fiber between the spools is cut.
A disadvantage of the above described methods of transferring fiber between spools is that the speed of the spools during transfer is not constant. The speed varies as the fiber is moved over the spool flanges and onto the base of the empty spool. In some designs, slots are cut in the flange for passing of the fiber in order to reduce the disturbance in fiber speed when the distributor leads the fiber over the flange. The slot, however, weakens the spool and increases its tendency to flex and distort, damaging the quality of the wound package. Both the collector mechanism and the snagger mechanism introduce large disturbances in the speed of the fiber as the fiber is suddenly grabbed. These sudden disturbances in the speed of the fiber greatly increase the tendency of the fiber to break, resulting in a costly shutdown of the fiber drawing machine. Another problem with both the collector and snagger mechanisms is that they occasionally fail to successfully transfer the fiber, again causing a costly shutdown of the fiber drawing machine. Furthermore, this tendency to miss/fail increases as the speed of the fiber increases. Given the unrelenting quest for higher drawing speeds, this tendency is clearly at odds with reliable high-speed machines.